Queen Victoria found Oliver Twist so "excessively interesting" that she pressed it on the prime minister, Lord Melbourne.

It was this response, from high to low, that made Dickens different. His books formed a direct connection with his readers that no one had ever had before, and few have had since. But that very connection meant that he, himself, was always on display, and for nearly 150 years, biographers and readers have puzzled over the secrets in the life of this complicated man.

Twenty years ago, Claire Tomalin's The Invisible Woman explained Dickens's second most traumatic life event, his vicious and very public rejection of his wife.

What no one had known at the time, however, was Dickens's childhood trauma, when his father was imprisoned for debt and the boy was sent to work in a blacking factory. That scar remained so fresh that not even his wife and his children were told of it.

Dickens was born in 1812 in Portsmouth to a clerk in the navy pay office (and later the model for Mr Micawber).

Leaving school at 15, he worked as a clerk himself, and then a journalist. When, aged 24, he was invited to write what became The Pickwick Papers, he awoke to find himself famous. From then on, his work rate was prodigious -- The Pickwick Papers was still being written when he began Oliver Twist, and Oliver Twist was not finished before Nicholas Nickleby started to appear.

In between novels, Dickens was a magazine editor. He sat on committees for a variety of good causes. He also raised funds for many children of friends, left orphaned and destitute.

This was greatly at odds with his treatment of his own family. He resented his wife for her endless pregnancies (11 in 15 years), apparently overlooking his necessary involvement, and he resented his sons for having the comfortable childhoods he had lacked.

He found it hard, he said, to show his feelings to his children, but in fact, as Tomalin shows, really he found it hard to have those feelings, writing, after one son repeatedly ran into debt, to his brother, "I begin to wish that he were honestly dead".

And when Dickens fell in love with Nelly Ternan, who was his children's contemporary, it was not enough for him to separate quietly from his wife of more than two decades: he needed to proclaim to the world her flaws.

Yet, as Tomalin shows, he was also a man of charm and warmth. Her psychological analysis is acute, isolating that elusive something that made Dickens great.

There have been many biographies in the past, and no doubt more are in the pipeline as the bicentenary of Dickens's birth approaches. But few will have Tomalin's sympathy and insight for this tormented man.

Dickens can barely be captured on the page, but his messages of warmth and love have been understood by generations of readers. Now, in Charles Dickens, Tomalin shows the tormented, tragic man behind the jollity and hope.